On stochastic comparisons of finite mixtures for some semiparametric families of distributions

In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards.     

Electronic `how things work' articles: two early prototypes

The electronic encyclopedia exploratorium (E³) is a vision of a future computer system-an electronic book describing how thing work. Typical articles in E³ will describe such mechanisms as compression refrigerators, engines, telescopes, and mechanical linkages. Each article will provide simulations, three-dimensional animated graphics that the user can manipulate, laboratory areas that allow a user to modify the device or experiment with related artifacts, and a facility for asking questions and receiving customized, computer-generated English-language explanations. Some of the foundational technology is discussed, focusing on topics in artificial intelligence, graphics, and user interfaces. The initial prototype system and the technical lessons learned from it, as well as the second prototype currently under construction, are described     

Transitional cell carcinoma of the distal portion of ureter protruding into the sigmoid conduit six years after cystoprostatectomy

Bladder tumors develop after the diagnosis of upper urinary tract carcinoma in approximately 20% of cases, whereas the incidence of upper urinary tract tumor after the diagnosis of bladder cancer is low, approximately 2%. In a 64-year-old man who had undergone cystoprostatectomy treatment of bladder carcinoma 6 years previously, with the sigmoid conduit used for supravesicle diversion, a transitional cell carcinoma that developed in the conduit was not revealed with intravenous pyelography at regular follow-up intervals. The patient had only hematuria. After an obstructed left kidney, left ureteral stricture, and a filling defect in the conduit were observed radiologically and biopsy revealed a transitional cell carcinoma at the ureterosigmoid junction, the patient underwent left nephroureterectomy, partial resection of a third of the sigmoid conduit, and right ureteral reimplantation. The occurrence of upper urinary tract carcinoma after treatment of bladder cancer should be considered even in light of intravenous pyelography that shows no abnormality; and when such carcinomas occur in this situation, disease involving the conduit should be ruled out.     

Bone marrow and renal injury associated with haloalkene cysteine conjugates in calves

Almost 40 years ago, it was reported that cattle-feed which had been extracted with hot trichloroethylene and then fed to calves produced renal injury and a fatal aplastic anaemia. The toxic factor was subsequently identified as S-(1,2-dichlorovinyl)-L-cysteine (DCVC). These original findings have been confirmed, a single intravenous dose of DCVC at 4 mg/kg, or 0.4 mg/kg intravenously per day administered for 10 days to calves produced aplastic anaemia, and renal injury after a single dose of 4 mg/kg. The toxicity to calves of a number of other haloalkene cysteine conjugates has been examined to ascertain whether, like DCVC, they produce bone marrow and renal injury. Intravenous administration of the N-acetyl cysteine conjugate of DCVC produced renal but not bone marrow injury at a molar equivalent dose to DCVC, indicating that the calf can deacetylate the mercapturic acid and further that sufficient chemical had reached the kidney to be a substrate for the enzyme cysteine conjugate beta-lyase. However, intravenous administration of the alpha-methyl analogue of DCVC, which cannot undergo metabolism via the enzyme cysteine conjugate beta-lyase, was without toxicity at doses about five-fold higher than DCVC. These latter findings provide strong evidence that metabolism of DCVC via the enzyme beta-lyase is necessary for bone marrow and renal injury to occur. The cysteine conjugates of perchloroethylene and hexachloro-1,3-butadiene(HCBD) when given intravenously to calves at molar equivalent doses to DCVC, or above, did not produce either bone marrow or renal injury. In contrast, intravenous administration of the cysteine conjugate of tetrafluoroethylene (TFEC) produced severe renal tubular injury in calves without affecting the bone marrow. In vitro studies with these haloalkene cysteine conjugates showed, like DCVC, that they were good substrates for calf renal cysteine conjugate beta-lyase and toxic to renal cells as judged by their ability to reduce organic anion and cation transport by slices of calf renal cortex and inhibit the renal enzyme glutathione reductase. Calves were also dosed either orally or intravenously with HCBD to assess its toxicity. HCBD at higher molar equivalent doses than DCVC produced mid-zonal necrosis in the liver, renal tubular necrosis but no bone marrow injury in calves. The key findings emerging from these studies are (1) that none of the other cysteine conjugates, at molar equivalent doses to DCVC and above, produce bone marrow injury in calves, (2) TFEC produced only renal injury, suggesting that sufficient of the other conjugates had not reached the kidney for metabolism by beta-lyase to produce cytotoxicity and (3) that HCBD itself is more toxic than its cysteine or mercapturic acid conjugate, suggesting that pharmaco-kinetics and disposition are important factors in determining the toxicity of these conjugates to calves. Further studies are needed to understand the basis for the selective toxicity of DCVC to the bone marrow of calves.     

Probabilistic approach to some problems of system safety

Measures of direct importance of unrepairable system components, based on the multilinear expansions, are introduced. Various characteristics of system quality of performance are discussed. Cases of binar and multistate components are studied. The measure of specific importance, considering the cost of reliability component's improvement, is defined. The multilinear expansion for a system of multistate components, giving the possibility to estimate measures of the direct importance of components and levels of components performance as well, is discussed. The limit transition to continuum structures is performed. Some measures of importance for repairable systems are introduced.     

Lung cancer among steelworkers in Ontario

A population-based case-control study was carried out to follow up observations of increased lung cancer risk in the steel pouring areas of two Ontario steel mills. Study subjects were all men, aged 45-75 years, who died of lung cancer in the cities of Hamilton or Sault Ste-Marie, Ontario from 1979-1988. Nine hundred sixty-seven lung cancer victims were matched with 2,827 control subjects who died of other causes. Work histories were provided by the employers of steelworkers. In comparison with other residents of their cities, the relative risk of death from lung cancer was 0.85 (95% confidence interval [CI]: 0.58-1.23) for steelworkers in Sault-Ste Marie and was 1.10 (95% CI: 0.89-1.37) for steelworkers in Hamilton. In internal comparisons within the steel companies, increased lung cancer risk was observed among foundry, coke oven, and pouring pit workers. Retrospective hygiene assessment suggested that the increased risk of lung cancer among steel pourers might be related to the use of tar-based mold coating agents or to exposure to mineral fibers.     

Evaluation of a workplace technology for mental health assessment: A meaning-making process

This paper describes the results of a summative evaluation conducted to explore the usability and acceptability of an automated telephone-based technology, designed and developed as a screening tool for mental health disorders in the workplace. The system screens employees for symptoms and subsequently provides educational information and referrals to improve mental health and enhance productivity. The qualitative evaluation was a sub-study of a larger randomized controlled trial (RCT). We conducted in-depth interviews with 15 individuals who participated in the RCT and had used the system. A phenomenological theoretical framework was utilized to analyze the narrative data. Results indicated that participants had mostly positive experience with the system and perceived it as a confidential program that allowed them to reflect on their symptoms without inhibition, fear of judgment or embarrassment. We also learned that asking mere questions about mental health symptoms can be a positive, instructive and possibly a restorative experience. There is a likelihood that for many participants, exposure to questions about their emotional and mental distress validated their feelings about their symptoms and was sufficiently compelling to promote help-seeking behavior. This evaluation study demonstrates that computers can be utilized in the workplace as effective screening and educational tools to improve employees’ mental health.